HESI A2 Anatomy and Physiology Quizlet

Correct Answer: A

Rationale: The correct answer is A: Melatonin. Melatonin is a hormone produced by the pineal gland that plays a key role in regulating the sleep-wake cycle. It helps control the body's internal clock and signals the brain when it's time to sleep. Melatonin levels typically rise in the evening, promoting sleep, and decrease in the morning, promoting wakefulness. Summary of incorrect choices: B: Insulin - Insulin is a hormone that regulates blood sugar levels, not the sleep-wake cycle. C: Cortisol - Cortisol is a stress hormone that helps regulate metabolism and immune response, but it does not directly control the sleep-wake cycle. D: Thyroxine - Thyroxine is a hormone produced by the thyroid gland that regulates metabolism, growth, and development, but it is not directly involved in the sleep-wake cycle regulation.

Correct Answer: B

Rationale: The correct answer is B: Glucagon. When blood glucose levels are low, the pancreas releases glucagon to stimulate the liver to convert stored glycogen into glucose, raising blood sugar levels. Insulin (Choice A) is released in response to high blood glucose, promoting glucose uptake by cells. Cortisol (Choice C) and adrenaline (Choice D) are stress hormones and not directly involved in regulating blood glucose levels.

Correct Answer: B

Rationale: The correct answer is B: Pivot joint. In the neck, the pivot joint allows for rotational movement by articulating the first and second cervical vertebrae. This joint structure enables the head to rotate from side to side. A: Hinge joint is incorrect because it allows movement in only one plane, like the elbow or knee. C: Ball and socket joint allows for a wide range of motion in multiple directions, like the hip or shoulder. D: Saddle joint allows for movement in two planes, like the thumb joint. The specific rotational movement in the neck is facilitated by the pivot joint, making it the correct choice.

Correct Answer: B

Rationale: The correct answer is B: Mitochondria. Mitochondria are known as the powerhouse of the cell because they are responsible for energy production through the process of cellular respiration. They produce ATP, the main energy currency of the cell. The other choices are incorrect because the nucleus is responsible for storing genetic material, ribosomes are involved in protein synthesis, and the Golgi apparatus is responsible for packaging and transporting proteins. Therefore, only the mitochondria play a direct role in energy production within the cell.

Correct Answer: C

Rationale: The correct answer is C: Veins. Veins carry blood back to the heart from various parts of the body. Blood in veins is typically low in oxygen and high in carbon dioxide. Veins have valves to prevent backflow of blood. Arteries (A) carry blood away from the heart, capillaries (B) facilitate exchange of nutrients and gases, and lymphatic vessels (D) are part of the lymphatic system that helps with immune function, not blood circulation.